The largest and best supported Jaguar cars enthusiast site on the Internet!

Serving Enthusiasts since 1993
The Jag-lovers Web

Currently with 3,166 members

Service Bulletins 1948-54 (XK120)
Compiled by John Elmgreen, Sydney, NSW Australia 5-96 ©John Elmgreen
Comment notes added by Bruce Carnachan and Rob Reilly
Not for reproduction




SB 46 - May 49: Advance information re XK120: This is the first I have re the XK120 and is headed "Advance Information on Mark V and XK Super Sports Models". It sets out details of the rubber bushes used in the suspension, namely the front and rear suspensions and shock absorbers.


SB 57 - Nov 49: Front suspension: The thread bearings at the ends of the track rod and the steering idle spindle were slotted with split pins initially, but from and including 660015/670025 were fitted with plain nuts and tab washers.


SB 65 - Apr 50: Valve timing procedure: Commencing with engine no. W.1124 (i.e. first 123 engines were otherwise) the procedure is that the special gauge be used for setting the valve timing. Previously, the method was to line up the keyways on the cams and the front cam bearing caps.

JE note: This must mean that the valve timing gauge was not fitted to the tool kit of earlier cars.

stated that there were 2 versions of the valve timing gauge:

- C.3993 supplied with tool kits (soft steel, for occasional use) "and supplied, packed in the tool kit, with cars now leaving the Works".

- C.4015 general service use (hardened and ground).

Valve clearances were specified at .006 inlet / .008 exhaust cold. The timing with special clearance of .010 was inlet opening 15 deg before TDC, exhaust closes 15 deg after TDC.

Reference was also made to an amendment required to the handbook, described as the "Operating, Maintenance and Service Handbook for 3-1/2 litre XK.120 Super Sports Models 1949", being for setting the ignition timing (page 37, para(b)).


SB 66 - Apr 50: Throttle restrictor: Advised that a throttle restrictor was being fitted to XK120 cars to prevent their being "run at excessive speed during their early life", in the form of "a stop on the underside of the accelerator pedal" secured to the pedal by a setscrew which is in turn locked by a wire and lead seal. The stop is to be removed at the time when the first service is carried out, that is, after the first 750 miles." No chassis numbers nominated.

Front brake air scoops: Announced that 2 blanking plates C.4292 would "in future be issued with each car, to be fitted, when considered necessary, in place of the normal stone guard, Part no. C.3527." It was also noted that the scoops themselves were to avoid brake fade. No chassis numbers nominated.

JE note: This must also mean that only cars from this time had the blanking plates fitted to the tool kit.


SB 71: August 1950 - Fitting of air cleaners as standard from that date on, and considered desirable to be fitted to earlier cars, already delivered but not fitted with air cleaners. To be supplied on earlier cars free of charge if purchaser supplies the early chassis number. All the way back to 660001 and 670001.

BC note: Walter Hill's car 670001 did not have them. Also, I find no reference to the change from tall carbs to the shorter version of the S.U. Both are called H-6 and the 1-3/4" throat. I have seen the air cleaner on an earlier steel bodied 1950 XK 120 with the tall piston damper housing. But a friend's car, #671000 has the short housing S.U.s, and a look through the Service Bulletins makes no reference to the change over.

RR note: Bob Tucker's car 670178 also does not have air cleaners.


SB 72 - Dec 50: Newton front shock absorbers: noted that the filler plug "has been deleted on Newton front shock absorber units now being fitted or supplied as spares." No chassis numbers nominated.


SB 74 - (undated, assumed c Dec 50): Valve clearance adjustment pads: announced an increase in the range available, and a change of marking from numerical to alphabetical (A-S).

Front engine mounting packing plates (RHD): noted that RHD cars were fitted with 2 packing plates between the right hand side rubber mounting and the mounting bracket, to give adequate clearance between the steering column and the rear carburetter.


SB 88 - Jan 51: Screws in rear wheel arches: Announced that "it has been found that on some XK.120 bodies metal screws of unsuitable length have been used to fasten internal body fittings and protrude into the rear wheel arch ... ". Recommended that they be cut, or replaced by round head bolts fitted in the reverse direction with a nut and lock nut inside the boot.

JE note: seems that this was an error in fitting from the factory. Apparently "bodgy" bolts fitted in reverse might therefore be correct!

RR note: possibly refers to screws for fuel filler hose cover, tire pump clips or tool roll strap which could cut a rear tire sidewall.


SB 89 - Jan 51: Brake linings: announced that from 660551/671097 linings became Mintex M.14, with a lower coefficient of friction than M.15 fitted to earlier cars. The later linings would require higher brake pressure, and a modification could be made to the location of the hole in the pedal lever to increase the leverage and reduce the effort required.


SB 90 - Mar 51 Rear Axles (ENV): axle casing - Note that the number was stamped on the top side of the axle nose piece.

JHS.1 - JHS.1602: casing part no. A.254/1 used for axles C.3452/3821/4460/4462 (various ratios): these had a packing piece C.3829 between the rear spring and the spring seat on the axle casing.

JHS.1603 - on: casing part no. A.259/1 used for axles C.3452/1, 3821/1, 4460/1, 4461/1, 4462/1. Casing has a modified spring seat with which the packing piece is not used.

JHS.1-JHS.1839: longer rear axle shafts (butted together) used (part no. A.259/11).

Thereafter: shorter shafts A.272/11, with spacer block.

Due to the different lengths, the shafts are not interchangeable.


SB 92 - Mar 51: Handbook / Service Vouchers: Commencing with cars supplied with the "revised Green cover Operating, Maintenance and Service Handbook and the BLUE cover Service Voucher booklet" the Service Voucher procedure was varied with only one service voucher being issued (500 miles service). The service was more extensive than before. The original handbook was described as having a yellow cover with orange covered Service Voucher booklet.


SB 93 - Mar 51: Maintenance: standard schedule (as amended) was set out here (one page) with details of work to be carried out each 2,500, 5,000 and 10,000 miles. Details of grease nipples were shown as follows:

4 - steering tie rods (left and right)

1 - wheel swivel (right hand)

1 - foot brake pedal boss

1 - fan bearings

1 - water pump bearings

2 - handbrake cable

4 - rear spring gaiters (JE note: check this for 150: no gaiters?)

2 - universal joints (propellor shaft)

1 - splines (propellor shaft)

4 - road wheel bearings.

The total of grease nipples was therefore 21.


SB 95 - Jun 51, 2nd issue Jun 52: Competition Modifications. This Service Bulletin is well known and often quoted in the usual XK books. The mods included engine mods (high lift cams, lightened flywheel etc.), dual exhaust, clutch, suspension, brakes, rear axle ratios. The later issue included further amendments.


SB 95A - Apr 53: C type Head: This was announced in this SB. The main features were described as revised porting, 1 5/8" diameter exhaust valves, and enlarged valve throats. It was supplied with valves, springs, high lift cams and rocker covers but without manifolds and was available on "an outright sale basis only" and with limited supply. [I take it that this meant that the parts alone could not be bought, and that you could not have your existing head modified by the factory). The SB then makes it clear that this was exactly the same head as used for a C type. If for an XK120 and 2 inch carbs were desired, the manifold would be C.6007. The original manifold could be used for the 1 3/4'" carbs. The assembly complete was SD 1025, retail UK price UKL 150. The 2 inch inlet manifold C.6007 was UKL 6/13/- and the 2 inch carbs were C.7805 (front) and C.7806 (rear) each for UKL 18.


SB 95B - Apr 53: Close ratio gears: close ratios gearboxes were now announced to meet the needs of those using 120s in competition; they were available only for JH and JL gearboxes. What was supplied were alternative Constant Mesh Gears, which resulted in closer intermediate gear ratios, sub-assembly constant mesh pinion C.6658 for UKL 9/17/6 and constant mesh wheel C.5826 for UKL 7/19/-. The ratios were then compared as follows:

Standard: Close ratio

1. 3.375 2.98

2. 1.982 1.74

3. 1.367 1.21

4. Direct Direct


SB 97 - Nov 51: Lubricants: [Note: this may be relevant to what appears on the car's ID plate]. Recommended lubricants were to be amended to read as follows:


Water Pump, Fan, Propellor Shaft Spline, All chassis nipples, Wheel bearings


Vacuum Mobilgrease No.5

Wakefield Castrolgrease WB.

Shell Retinax A

Essolube High Temp Grease

Prices's Belmoline H.M.P


Front Shock Absorbers: For "service replacement purposes" the settings for the front shocks were revised from B (?).6.SC.2 to UE.6.SC.2. Units having the UE SC.2 setting are identified by " a blue metallic paint spot". The modified units were to be fitted only in pairs.

Heater adaptor in block: From and including W.3686, (and Mk VII A.3303), and a few engines prior to those numbers, "a boss is incorporated in the cylinder block casting at the rear left side of the engine above and slightly forward of the oil sump dipstick, this boss being fitted with an internal hexagon plug, being tapped 1" American standard pipe thread for fitment of a U.S. standard engine heater element No. 7, manufactured by The Electric Heating & Manufacturing Co. Ltd., when so desired."

Air conditioning Installation: From 660911 / 671493 air conditioning unit without demisting and defrosting of the windscreen is fitted as standard. Operating instructions were per page 26 of green Handbook (except for demisting/defrosting)

Wiring diagrams: These were circulated with this, the references being W.94601 for XK120 home and RHD export, and W.94641 for LHD.

Sumps: These were changed from and including W.3635 and W.3593-3596 to the Mk VII stepped type sump, with the capacity now at 21 Imperial pints (US 25 pts, 12.2 litres) for the sump, and 24 Imperial pints (28 pts US, 13.5 litres) for the whole engine.


SB 99 - May 54 (revised version per amendments in SBs118, 129, 136, 148). The recommendations superseded all earlier ones and were:


Compression Ratio 7 to 1

Standard Weak (high lift, racing)

SU Carb Needle

Super Sports RF RG

Coupe Models WO2 WO3

(fitted with remote air cleaner)

Champion Sparking Plug type L10S L11S


Compression Ratio 8 to 1

Standard Weak (high lift, racing)

SU Carb Needle

Super Sports RF RG

Coupe Models WO2 WO3

(fitted with remote air cleaner)

Champion Sparking Plug type N8B NA10


Compression Ratio 9 to 1

Standard 2 inch carbs Weak

SU Carb Needle

Super Sports RB VR VE

Champion Sparking Plug type NA12 NA12



Rear Axle lubricant: stressed the importance of using the right oil: recommendations were:


Vacuum Mobilube GX 90

Wakefield Castrol Hypoy

Shell Spirax 90 B.P.

Essolube Expee Compound 90

Price's Energol Hypoid 90


SB 101 - undated timing chain tensioner dealt with.

Rear axle: on some cars, after 660935/671797 and 669003/679222 Salisbury rear axles of 3.77 ratio were fitted. They were distinguishable from the ENV by having a non-detachable nose piece, and with the filler plug situated in the cover at the rear of the axle casing.


SB 102 - Feb 52: Valve guide replacement: dealt with in detail. Tappet clearances were nominated to be .006/.008 for the XK120 (but .004/.006 for Mk VII). Heads: Valve seat angles were 30 deg inlet and 45 deg exhaust.


SB 108 - Jun 52: part nos. of the parts mentioned in 102 have been changed as follows:

valve guide inlet C.7260 supersedes C.5744/2

exh C.7261 C.5745/2

valve seat insert inlet C.7258 C.2165/2

exh C.7259 C.2164/2

tappet guide C.7262 C.5746/2


SB 103 - Feb 52: Throttle restrictor: advised dealers to check that when the throttle restrictor was removed at the first service, that full throttle was available.


SB 104 - Feb 52: Gearbox: from 660935/671797 and 669003/679215, a new gearbox was introduced with a short mainshaft without the rear extension. This required in consequence a longer prop shaft and different length speedo cable. The new gearboxes were SL or JL, not interchangeable with the earlier SH/JH series. It was further noted that the Mk VII and XK120 short mainshaft gearboxes were not interchangeable.

RR note: SL/JL gearboxes for Mk VII did not have the provision for the rubber mounting parts on the tailcase, necessary for XK120.


SB 105 - Apr 52: Pistons: recorded that 2 alternative types of pistons were fitted (in sets), either "Brico" semi-split skirt type, or "Aerolite" solid skirt types. Comments re reducing skirt clearances on the Brico type.

Heads / valve and tappet guides: from W.4483 (Mk VII A.6536) the valve and tappet guides were all modified to permit the fitting of high lift cams without modification. For engines W.4012-4482 the only the inlet valve guides were not modified (the others were). For all earlier engines, the required mods were set out in 95. Gearboxes: due to supply problems, it had become necessary to revert to the original type long mainshaft gearboxes for some cars (SH/JH). Therefore stating the full gearbox number was important.

Oil filter: from W.4383 onwards, the Mk VII type oil filter was fitted (C.4767).

Engine breather pipes: if they butted onto the chassis, and were blocked in this way, they were to be shortened.


SB 106 - Apr 52: Self adjusting front brakes: from 660980/672049 and 669003/679622 these were fitted, with a tandem type master cylinder. The master cylinder was 1" and the wheel cylinders front and rear were all 1 1/8". This contained a full description and servicing details of the whole system.


SB 107 - May 52: Wheels: in the "near future" road wheels having wider rims were to be introduced, 5-1/2" instead of 5". The new, wider rim could be identified by "two depressions in the wheel rim, one on each side of the valve hole, these depressions not being present on the existing 5" wheel rim." Overall track was increased 1/2", and for the XK120 became 4' 3-1/2" front and 4' 2-1/2" rear.

Fan, water pump: from W.5465, 6 bladed high speed fan and integral fan pulley and hub are fitted. Except for the fan and by pass hose connection, the water pump assembly and fan belt are interchangeable with the Mk VII ones from A.2001 onwards. The XK120 fan however is of smaller diameter than the Mk VII and therefore NOT interchangeable.

Shell Oil - lubricant recommendations: With the change in oil grades of Shell Mex and B.P. Ltd, the following lubricants replaced the previous recommendations:

Engine summer 32deg - 90deg F X-100 30

winter below 32deg F X-100 20/20W

tropical above 90 deg F X-100 40

Gearbox, carb dampers, distributor,

oil can lubrication X-100 30

JE note: did the ID plates change accordingly?

Salisbury rear axles: on earlier cars (prior to 660977/671985, 669003/679541) there were BSF threads used for certain bolts (gear carrier cover and differential cap); later cars used ANF threads.


SB 108 - Jun 52: Front shock absorbers: Newton telescopics with revised valve settings fitted, part no. C.7183, from 660980/672049, 669003/679622. The later type is 2 1/8" (? 2 1/2") diameter instead of the 2 3/4" diameter of the early type C.3035.

Rear shock absorbers: Girlings with revised valve settings fitted from 660986/672280, 669003/679729, new part no.s being C.7214 (RHS) and C.7215 (LHS), with Girling part no. 71 RH and 72 LH stamped on the top of the shock absorber body.


SB 109 - Sep 52: Special Equipment XK120 models announced: identified by an S prefix to chassis and S suffix to engine number. listed 18 items incorporated (to be reproduced in full). In addition, there were options (intended for racing). With the high lift cams, valve clearances of .006/.010 were stipulated. JE note: did the ID plate change for these cars? Also the rear track altered from 4'2" to 4'3 3/8". There were also racing recommendations made.

Carb needles (Trinidad): carb needles recommended for Trinidad cars were RG. No explanation was offered.

Spark Plugs (Hong Kong, Switzerland): Hong Kong, 7:1 engines: Champion L.10, Switzerland 8:1 Champion N.8.B. No explanation was offered.


SB 110 - Oct 52: Salisbury rear axles: to be fully reproduced.

Woodwork faults: to be fully reproduced.

Battery - level device: to be fully reproduced.


SB 111 - undated: Tandem master cylinders: there had been complaints of brake failure that had been found to be due to adjusting the rear brakes the wrong way (clockwise instead of anti clockwise), and also problems with dealers not following instructions per 106 re the assembly of the master cylinder. Noted that brake linings for cars with self adjusting front brakes were Mintex 1/4". These were fitted from 660980/672049, 669003/679622.


SB 112 - Oct 52: Oil sump level unit: deleted from W.6149 inclusive. Blanking plate C.4492 and gasket C.937 fitted, and oil level switch deleted. [JE note: this obviously affects the dashboard/instrument panel].

Demister: provided for from 661026/672963, with vents fitted to base of screens and connected to the heater unit by flexible hoses. OTS now same as FHC in this regard.

Side lamps: new style (integral side lamps) from and including 661025/672927, front wings now part no. BD 7929/30.

"Cars scheduled for export are fully wired for flashing indicators and have relay units fitted. Owing to shortage of supplies Tung-Sol unit part number 241D is not included for certain countries, and it is the responsibility of the Distributor to ensure that unit is obtained locally and fitted prior to delivery." [JE note: this seems an odd state of affairs - more likely to be obtained locally than by Jaguars themselves? What countries involved here?]

Jaguar gearbox: "A modified gearbox top cover (C.6878) and reverse striking rod (C.7358) are fitted to Jaguar gearbox No. JL.13154 and future." The complete top cover was interchangeable, but the old reverse striking rod C.878 was not. [JE note: has this got anything to do with the change from Moss boxes to Jaguar made gearboxes?]

Headlamps: "Messrs Joseph Lucas Limited will in future supply a conversion set part number 553962 to enable British type head lamps to be converted for the use of U.S.A. type sealed beam units. These conversion sets will also be obtainable from Lucas Electrical Services of sans-serif and Los Angeles."

Starting carb: There were obviously problems with this item as this recommended 3 different modifications:

(1) If the carb cut out too hot or too cold: the thermostatic switch should cut out at about approx. 35 deg C. A modified switch was now available if the switch cut out too high or too low a temp, the new one being C.2474 and identifiable by a "green spot situated on the front cover". [JE note: did the switch look any different otherwise?]

(2) If the carb failed to cut out at all:

(a) there seems to have been a problem with the cork washer at the far end of the central tube; if after dismantling the plunger the impact washer is either dark green or natural cork, then replace it with a red fibre washer 3133/1;

(b) also replace the plunger part no. 3205 with a new "improved machined type" also 3205.

Front shock absorbers: non-original types: if non-standard dampers were fitted (i.e. other than the recommended Newton or Girling) with "a longer fully extended length than the standard type", they could be dangerous, as the steering could become locked in rebound position, with the resultant breaking up of the upper wishbone ball joints. The correct XK120 fully extended length was 16 1/16" (40.8 cm) between the centre of the bottom eye bush to between the top mounting bushes.


SB 114 - Dec 52: Paint (synthetic): "All cars now being produced are sprayed with Synthetic Enamel. This process commenced from the following Body numbers:- " XK120 OTS F 5272 on, XK120 FHC J 2375. [JE note: check the approx. equivalents in chassis numbers, RHD and LHD.] Also some bodies prior to these numbers were also so treated (selected numbers from F 5082 OTS and J 2223 FHC). Note: this section to be mostly reproduced in full text.

JE notes re chassis numbers / body numbers / dates, late 1952:

660999 F 4582, ch compl 25 Jun 52

661095 F 6247 cc 15 Jul 53

Cannot find one RHD XK120 to Aus with a body number in the F 5000 series - must have all gone to the USA!

Re FHCs: all Aus RHD cars were after the stated body no.s and therefore all were Syn painted. Even 669012 was body J3075.


SB 115 - Dec 52: Windscreen washers: Noted fitting from chassis nos. 661037 (+026, 028,029) / 673009 and 669003/680271 (+ 167-9). "Trico". "This vacuum operated windscreen washer comprises a glass water contained mounted on the engine side of the scuttle which is connected to jets at the base of the windscreen. Water is delivered to the jets by a vacuum operated pump incorporated in the water container cap. The top pipe of the pump is connected to the inlet manifold via a control button on the instrument panel; the pipe on the side of the pump is connected to the two jets at the base of the windscreen."

To operate: "Press the chromium plated control button fitted to the instrument panel for a few seconds. Release button, when two fine jets of water will strike the windscreen at points one or two inches below the upper edge and in the centre of the area of wipe provided by the windscreen wiper."

Later: "Do not add radiator anti-freeze solution to the water as this is detrimental to the washer mechanism."

Filling: "Fill the container 3/4 full with clean water."

Solvent: "It is recommended that 'Trico Windscreen Washer Solvent' No. X.A.W.30 is used through the year."

Shock Absorbers: "To simplify service replacement, Girling telescopic shock absorbers types CDR/1 and CDR/6 (Part No.s C.4317 and C.6832 respectively) should be replaced by type CDR5/7 (Part no. 6833) in ALL countries." (These were now standard except for UK and USA).

Prop shaft access plate: "XK120 cars are now fitted with a detachable plate to allow easy access to the front universal joint and spline nipples of the propellor shaft. The plate is situated on the right hand side of the gearbox cowl and can be detached after lifting the centre carpet and removing the five securing screws."

Rear Road Springs: From 661040/673320 669003/680397 stiffer rear road springs C.5721 (as fitted to the SE models) were fitted. Has 5 leaves 7/32" thick and 2 leaves 3/16" thick as against 3 leaves 7/32" thick and 4 leaves 3/16" thick for the earlier type C.3661. Interchangeable in pairs. Note: the part no. of the spring was stamped on the bottom leaf.


SB 116 - Dec 52: Road wheels: new road wheels 5 1/2" K x 16" fitted (with 5 1/2" rims) except of course for WW cars. See 107. Chassis no.s involved: from and incl: 661042/673298, 669003/680477. The same change was implemented for the Mk 7 and it was noted that tyres of section up to 7.60 could be fitted, provided that wheel arch clearance was checked (and arches modified if necessary).

Keys: Cars now in production were provided with 2 types of keys (incl Mk VII):

- round headed key for ignition, doors (FHC) and petrol filler

- rectangular headed key for the bootlid and cubby box lock (glove box).


7:1 - from W.6539, fitted with distributor C.5442 (standard cams) or C.5468 (high lift contact breaker cams), the latter being Lucas 40198D or GC.4740249/B stamped on body)

8:1 - from W.5509, fitted with distributor C.5443 or C.5469 (high lift contact breaker cams).

Mk VII engine nos.: B series now commenced (B.1001). Note that no difference in the engine specifications was mentioned.

Sump plugs: where the threads are damaged, an oversize plug C.7727 with a 3/4" ANF thread was now available. The hole was to be redrilled and tapped to take the new plug.

Gearbox: From JL 13834 / SL 6313A a stop pin is fitted to the first and second speed synchronizing sleeve to prevent overtravel on engagement of first gear, with the possible release of the synchro balls and springs. The stop spring is situated at the near edge of the synchronizing sleeve in line with the open hole for the locking plunger and ball. The new sleeve should be used when repairing an older gearbox.

RR note: The stop pin is actually a rivet which prevents getting stuck in first gear. On gearboxes made previous to this change it was common for repair shops and even authorized dealers to fix it by wrapping a piece of wire around the shifter fork operating shaft, or putting a washer on it. The problem has been noted among AC, Aston-Martin and Morgan owners as well.


SB 116A - Dec 52 (restricted circulation, to Home distributors and dealers).

Decarbonising: In response to statements from Mk VII owners that dealers had been telling them that decarbonising would be necessary between 4-6,000 miles, this stated that this was incorrect and that decarbonising should be carried out only when the compression was unsatisfactory or there was loss of engine performance, and that the cars were quite capable of 30-40,000 miles before there was any real need for decarbonising or valve grinding. The following were the correct compressions (in lbs/in2) with the plugs removed, the water outlet temp at 70 deg, and rotated on the starter:

Mk VII XK120

7:1 110 105

8:1 120 120

JE Note: I am not aware of what was the difference between the engines that gave different compression figures here. Different cam timing etc.?


SB 117 - Jan 53:

Specifications: provided to dealers - "To provide Distributors and Dealers with a record of the specification of individual cars, which may be required for Service purposes, a label giving this information is now attached to all new car invoices issued to Distributors. Will all Distributors please ensure that their Service and Spares departments record this information ... The information given is as follows:

Commission Number

Engine Number

Piston Type and grade Note. Type L/P denotes pistons, Part No.

C.2426 (8:1 comp ratio) or C.2265 (7:1 comp ratio)

Type C denotes pistons , Part No. C.3087 (8:1 comp. ratio) or C.3086 (7:1 comp. ratio)

Also note piston grades reading from left to right are for numbers 1 to 6 cylinders (No. 1 cylinder at rear of engine).

Gear box Number

Axle type, Number and Ratio

Shock Absorbers Part Numbers, Front and Rear.

Speedometer Number.

Body Number.

Colour Note. BD denotes British Domolac paint and P.J. Pinchin Johnson paint

Trimming colour

Headlining colour

Key numbers of Ignition, Door, Boot

Special Equipment

JE note: Brylaws, the Sydney, Australia dealers, kept this information on their "car cards", copies of which are held for cars they sold new.

High Lift Camshafts

Set out instructions for avoiding fouling of pistons with cams when high lift cams were fitted.

Hood: rear window

"From Chassis numbers: 661046 right hand drive, 673396 left hand drive, a modified type of hood rear panel is fitted. This type of panel is opened by unzipping both sides in an upward direction; unzipping the base of the panel and disconnecting the fastener. The panel is retained in the open position by raising the bottom edge and attaching the fasteners to the studs provided on one of the hood sticks. It should be noted that it is particularly important, when stowing the hood, to prevent the fabric from being trapped by the hood sticks."


SB 118 - Feb 53: Carb needles, FHC: FHC with the remote air cleaners now being fitted with WO2 needles instead of RF. WO2 was weaker and avoided richness at certain speeds, resulting in improved petrol consumption.


SB 119 - Feb 53: Petrol: improved Noted the introduction of improved petrol in the UK - approx. 80 octane Motor Method or 90 Octane Research Method in Great Britain. Standard /pool grade petrol was noted as being about 72 Octane (Motor Method). For 7:1 engines, "slightly improved performance, smoother running and possibly improved petrol consumption" could be obtained with the premium petrol with the same ignition settings and revised carb adjustments. A definite improvement could be obtained by fitting 8:1 pistons however.


SB 121 - Mar 53: Coolant Loss: It was interesting that the factory noted that a car run from cold to normal operating temperature would lose 1.7 Imperial pints of water, and that that was normal. Further, if there were serious water loss, it was recommended that the head gasket be replaced with the Klingerite type C.2250 with jointing compound both sides (for cars with the cast fan), and for later cars (with the pressed metal fan and high speed fan pulley) it was recommended also that the head gasket be replaced and that a new impellor C.7674 be fitted. The new type of pump was fitted from W.7199, and the new head gasket from W.7207 (Mk VII B.2451). Impellor C.2458 (4 vane) was superseded by C.7674 (5 vane).

Single exhaust for S.E. FHC cars: From 669005/680738, a single exhaust was fitted to SE FHC cars, although the OTS continued with the dual type. No reason was stated for this.


SB 122 - Apr 53: Rear axle: 3.54 for 3.77: From 661054/673695, 669007/680880, 667002/677016 cars were fitted with a Salisbury 4HA rear axle of 3.54 ratio rather than 3.77 as before. Then set out the rpm for mph calculations for the 3.54 as the standard ratio.

JE Note: was this not the information on the additional sheet glued into the handbook? Would this therefore date the handbooks from this date?


SB 122A - Apr 53: Continental Touring Kit: This was for "Home Trade Circulation" only, so presumably the kits were only available in GB. "A comprehensive kit of emergency spares items, packed in a special container, is available for the purpose of assisting Jaguar owners who contemplate a Continental Tour. These kits are sold on a "sale or return" basis and full allowance will be made (upon their return) against each unused item." Such kits were available for Mk IV, V VII and XK120 models. The XK120 kit was Pds 24/1/10 plus 7/3 purchase tax on bulbs, a total of Pds 24/9/1. There was no further elaboration on what was included in the Kit.


SB 123 - May 53: Crankshaft damper: New damper C.8020 now fitted from W.8381, being malleable iron superseding the cast iron type C.2464. However, a steel damper C.5809 was recommended where the engine was modified per 95 (for operation at increase rpm).


SB 124 - May 53: Brakes: service recommendations, re easy driving after fitting new linings for bedding in. "Similar instructions to those given above are being included in the Owners Handbooks, and Sales and Service staffs should impress on owners, who are collecting a new car or a car which has had new brake linings fitted, the need for complying with those instructions."

JE Note: check the change to the Handbook wording.

Flywheel: lightened: Engine W.8275 and onwards has lightened flywheel C.5808 fitted as standard (being the same as fitted to SE cars and the C type). JE Note: what were the respective weights of the old and the lightened types?

Ignition settings: detailed here for XK120 7:1 and 8:1.

Flywheel: ring gear: Noted here that there were 2 3/4 deg between the centre of teeth here.


SB 127 - Jun 53: Brake Linings: Very late cars now had Mintex M20 linings fitted (from 661087/674076, 669034/681207, 667002/677492 onwards).

Self adjusting brakes: These were fitted from 660980/672049, 669003/679622, all DHC.


SB 128 - Jun 53: Speedo cables: Modified cables (not stated how modified) fitted from 661078/674006, 669021/681203, 667002/677286. New cable was C.5590 (same as Mk VII from the same stage), Smiths part no. SK.52091/42 and 60 inches long. It was interchangeable with the earlier type.

Rev Counter cables: Modified cables fitted here too, from 661075/673995, 669021/681200, 667002/677242, the OTS ("Super Sports") being C.5594 (Smiths SK.80710/1, 19 inches) and the FHC/DHC being C.5593 (Smiths SK.80710/1 - same part number for some reason - but 16 inches long).

JE note: It seems that the "cables" referred to here are inner cables, not the whole assembly, but check the parts book on this point. Or there is an error.

RR note: Smith's and Jaguar part no.s quoted here refer to the whole assembly.

Connecting rods: A new sort of con rod (C.7917, embossed on the con rod) was fitted from W.8643 onwards. This used cap bolt bosses of increased length and the washer C.386 originally fitted under the nut was not used. There had been 3 earlier types of con rods (C.2448, C.2438, C.5835).


SB 129 - Aug 53: Valve springs: Due to valve spring breakages, a new type of valve spring was being fitted (C.7136 outer, C.7137 inner) to SE cars from W.9487. The new springs were now the only replacement parts to be used whether for standard or high lift cams. They had a red paint stripe vertically on the outside of the spring coils (although certain earlier springs also had the red stripe). The dimensions were different from the earlier types, as follows:

C.2272 outer 1.775" C.7136 outer 1.937"

C.2271 inner 1.515" C.7137 inner 1.656"

Tappet guides and valve seat inserts: Temperature and time for heating of the head reduced from 450 deg F (232 deg C) to 300 deg F (150 deg C) and from 1 hour to 1/2 hour.


SB 130 - Aug 53: Water pumps - interchangeability:

Early XK120, to W.5464 - features: cast 5 bladed fan and separate pulley and hub - now use C.4946 (replaces C.3826, C.3870, C.4481)

Late XK120 - 6 bladed fan and integral pulley and hub - now use C.6746


SB 131 - Aug 53: Ignition suppression: "Note that all Home Market and Home leave cars are now fitted with ignition suppressors." (XK120 and Mk VII).


SB 131 - Sep 53: Valve clearances: Stated that the recommendation for high lift cam cars was now .006/.008", with standard cars the same (but Mk VII were .004/.006"). The earlier recommendations for high lift cam cars (per SB's 95, 109) had been .006/.010". JE note: does this explain in any way the modified ID plates on some cars, with the added small plate at the bottom of the standard ID plates?


SB 133 - Sep 53: Racing screens: Racing screens and cowls (BD4470-1) supplied as standard with SE cars would in future be supplied to special order only.

Gearbox: strengthened forks: Strengthened change speed forks were fitted from JL18457, 3 different parts (C.7724-5-6 replace C.913, 872, 904).


SB 136 - Nov 53: Carburetter part nos.: For ease of interchangeability, new part no.s were adopted for future use. C.5690-1 (early XK120 to W.4095) replaced part no. C.2367/A-B, and C.5692-3 replaced part no. C.5185-6.

Engine nos.: F series: These were announced in this Bulletin (F.1001 on).

Spark plugs: recommendation for all 8:1 engines changed from Champion NAS to N8B. They were fitted to all engines from F.1050.

Paint: additional colour: add to SB 114 British Domolac colour Red, ref no. Q 1089.


SB 139 - Jan 54: Torsion bars: revised adjustment method: Outlined in detail here. The clearance for the XK120 at the front cross member was to be 11-1/4 inches. It was noted that friction in the suspension could cause problems, e.g. with slow raising or depression of the suspension, a difference of as much as 3/4 inches could be obtained.


SB 140 - Jan 54: Valve clearances: revised: These were now revised for all cars to .004/.006 (had been .006/.008). C types and cars with high lift cams actually to be used in competition were to be .006/.010".

Cigar lighter: Modified type C.5631 fitted from 661151/674415, 669106/681271, 667161/678085. The new Mk 2 type could be identified by four indents on the chrome plated shoulder of the holder, and the element had a copper plated ejection spring. The new type was not interchangeable with the earlier type except as an assembly.

Gearbox: change speed forks: SL gearboxes were now modified from SL9984A with the same new change speed forks as earlier noted for the JL series i.e. C.7724-5-6.

Gearbox: close ratio gears: In future, gearboxes fitted with CR gears were to have the suffix CR added to the number (obviously not done earlier, so that fitting of CR gears would not have been recorded in this way). There was also an instruction that if CR gears were fitted in service, the suffix should be added to the gearbox and the ID (commission) plate.


SB 142 - Jan 54: High lift cams: instructions as to how to avoid fouling (superseding earlier on the same subject).


SB 143 - Jan 54: Salisbury axles: instructions re pinion adjustment set out.

Brake fluid: In future, fluid labeled "Genuine Lockheed Hydraulic Brake Fluid" and "SAE Spec. 70 R2" would be used for service. Colourless. Interchangeable with earlier fluids, referred to as "Orange Fluid", "No. 5 Brake Fluid" and "Special No. 5 Fluid". Factory used No. 33 fluid with a lower viscosity than 70 R2 for cold countries. JE note: is this an item on the ID plate re lubrication etc.?


SB 144 - Feb 54: Engine breather pipe: warning re blocking and symptoms.

Tyre pressures: Handling of the car was impaired if the high speed pressures of 35 psi were used for speeds considerably less than 100 mph.


SB 145 - Mar 54: Gearbox interchangeability: detailed list of interchangeable items for Mk V, VII and XK120 gearboxes. Notes that the gearbox for the XK120 cars had a platform incorporated in the rear end cover for mounting to the chassis (not required for Mk VII). SH and JH gearboxes were interchangeable except for the gear lever shape.

RR note: SH/JH gearboxes for Mk VII had the platform but it was not used, as they had rubber mounts on the bell housing instead. Mk V gearboxes had the platform and used it, but note that the input shaft is different from Mk VII and XK120.


SB 146 - Apr 54: Valves - inlet: new type fitted from F.2365 - part no. C.8248, identified by the depression in the valve head, the earlier type C.2246 having had a flat head.


See SB 149 - May 54: The modified inlet valve C.8248 had a thicker head, and was liable to foul the pistons even with the standard 5/16" lift cams.

Valves - exhaust: These valves (new C.8313) were also modified, but also the guides (new C.8312). The new valves had a stem of reduced diameter under the valve head to form a scraping edge inside the guide. The new guides were shorter (1 15/16 inches vs. 2 5/16 inches) without (the earlier) counterbore at the valve head end of the guide.

Clutch plate: new type C.8401 fitted from F.2726, carrying the Borg & Beck part no. 47627/46 marked on the lining. Interchangeable with earlier types.


SB 147 - Apr 54: Valves - exhaust - sticking: Found that sticking exhaust valves had been occurring where the head had the exhaust valve guide that protrudes into the exhaust port casting not surrounded by a boss formed from the exhaust port casting. A modification was set out (reducing the length of the guides).


SB 147A - Apr 54: Tyres - alternatives: advice to dealers re customers who want special tyres. No brands mentioned. Original equipment selected as the best all round performers.


SB 148 - May 54: Timing chain tensioner blade: modified type C.8245 fitted from F.2773. Hard chrome plated and polished. Interchangeable.

Tyres: Butyl type tubes: "Butyl" type rubber tubes fitted to some cars - they were black vs. natural rubber which were red. Could be repaired satisfactorily.


SB 149 - May 54: Cams - fitting precautions: The modified inlet valve C.8248 had a thicker head, and was liable to foul the pistons even with the standard 5/16" lift cams. Also when high lift cams were fitted, fully open valves would protrude below the head face.


SB 150A - Aug 54: Rear reflectors (UK): "Under the Road Transport Lighting Act 1953, it is compulsory with effect from 1st October 1954 for all cars to be provided with two rear reflectors." Cars supplied on and after that date were to have reflectors "incorporated in the glass of the tail lamps". There was a detailed set of 7 criteria for the reflectors to meet (distances, etc.). Details were provided for fitting reflectors to all past models. They were to be obtainable from Jaguar spare parts departments. The part no. for the XK120 was C.8746 (Lucas type RER 5) with self tapping screw. They were to be fitted to the boot lid, with the hole 1 3/8" in from the edge and 3 1/4" up from the bottom edge of the boot. They were approximately in line with the bottom line of the rear license plate. Other Jaguar models used different part nos. for reflectors.


SB 151 - Sep 54: Rear axles - Salisbury: tools: Tools (7 types) were now available from V.L. Churchill & Co. Ltd, London SE11.

Overdrive - tools: Tools available from V.L. Churchill & Co. Ltd also (11 types).


SB 152 - Sep 54: Rev counter cables: Modified cables fitted commencing 661165 (less 661166-9) /674929 (less 675031-607), 669158/681466, 667243/678305. The new type had "outer cables completely made of black polyethylene".


Super Sports FHC, DHC

Length 18-1/2" 16"

Complete C.8274 C.8272

Outer SK.80750 SK.80750

Inner SK.52108/185 SK.52108/16


Handbrake: Modified handbrake fitted commencing 661170/675763, 669185/681477, 667271/678390. No details other than that the lever (C.7905), rod (C.7906), and ratchet (C.8445) were now different. JE note: was this the bent handbrake lever fitted apparently only to very late cars?


SB 153 - Sep 54: Horn push - flat: Modified steering column control assembly fitted from 661172/675926, 669194/681481, 667280/678418. There was a list of the changed components, including the horn push (now C.4514, also 330682), lever assembly, stator tube (63 5/8" long). Mk VII was changed at the same time.

JE note: These flat horn cars are only the last few XK120s.

OTS RHD 5 cars only LHD 513 cars

FHC RHD 2 cars only 5 cars

DHC RHD 16 cars only 55 cars

totals RHD 23 cars LHD 573 cars 596 cars


SB 155 - Sep 54: Horn push and steering column controls: Lists details of earlier modification that applied to the following chassis numbers:

OTS 661025-1171 672927-675925

For the FHC and DHC, these parts were fitted from the first chassis numbers. There were details on which of these parts Lucas distributors would not be supplying.

JE note: so there were apparently 3 sorts of steering column controls - (1) early roadsters, (2) later roadsters; FHC and DHC from beginning (3) latest few cars (flat horns).




compiled by John Elmgreen, Syndey, NSW Australia 5-96

comment notes added by Bruce Carnachan and Rob Reilly



Please help support the move to the new site, and DONATE what you can.
A big Thank You to those who have donated already!



Go to our Homepage
Improve your Jag-lovers experience with the Mozilla FireFox Browser!

  View the latest posts from our Forums via an RSS Feed!

Jag-loversTM Ltd / JagWEBTM 1993 - 2024
All rights reserved. Jag-lovers is supported by JagWEBTM
For Terms of Use and General Rules see our Disclaimer
Use of the Jag-lovers logo or trademark name on sites other than Jag-lovers itself in a manner implying endorsement of commercial activities whatsoever is prohibited. Sections of this Web Site may publish members and visitors comments, opinion and photographs/images - Jag-lovers Ltd does not assume or have any responsibility or any liability for members comments or opinions, nor does it claim ownership or copyright of any material that belongs to the original poster including images. The word 'Jaguar' and the leaping cat device, whether used separately or in combination, are registered trademarks and are the property of Jaguar Cars, England. Some images may also be Jaguar Cars. Mirroring or downloading of this site or the publication of material or any extracts therefrom in original or altered form from these pages onto other sites (including reproduction by any other Jaguar enthusiast sites) without express permission violates Jag-lovers Ltd copyright and is prohibited
Go to our Homepage
Your Browser is: CCBot/2.0 (, IP Address logged as on 18th Jun 2024 19:08:10